Optical biosensors are powerful detection and analysis devices that have vast applications in biomedical research, healthcare, and pharmaceuticals. This paper includes design of a 2-dimensional photonic crystal based biosensor with line defect which can detect different components of blood. Analysis has been done for blood serum albumin, blood plasma, glucose, white blood cells and red blood cells. Analytical work has been done using Finite Difference Time Domain (FDTD) method. Modeling and designing of photonic crystal is done with the help of simulation tools MEEP and MPB. Simulation results shows different blood components like blood serum albumin, blood plasma, glucose, white blood cells, and red blood cells and their peak has been observed. It has been observed from the band structure that for little change in refractive index there will be a moderate shift in the frequency and hence it acts as a sensor.